1. Field of the Invention
Example embodiments generally relate to a transfer-fixing device, an image forming apparatus including the transfer-fixing device, and a transfer-fixing method, for example, for simultaneously transferring and fixing a toner image onto a recording medium.
2. Description of the Related Art
A related-art image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction printer having two or more of copying, printing, scanning, and facsimile functions, forms a toner image on a recording medium. For example, an electrostatic latent image formed on an image carrier is made visible with toner as a toner image. The toner image is then transferred from the image carrier onto an intermediate transfer member (e.g., an intermediate transfer belt). The toner image is further transferred from the intermediate transfer member onto a recording medium in a transfer process. A fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium in a fixing process.
Such image forming apparatus, in which the transfer process and the fixing process are performed separately, may form a faulty image when the toner image is transferred onto a recording medium having a rough surface. For example, when the rough recording medium contacts the intermediate transfer member, the intermediate transfer member may not fully conform to irregularities in the rough surface of the recording medium and minute gaps may be formed between the intermediate transfer member and the recording medium. Accordingly, faulty electrical discharge may be generated in the minute gaps and the toner image carried by the intermediate transfer member may not be transferred onto the recording medium properly. As a result, a faulty image is formed on the recording medium.
To address this problem, one example of a related-art image forming apparatus includes a transfer-fixing device for performing the transfer process and the fixing process simultaneously in a transfer-fixing process. In the transfer-fixing device, a pressing member contacts a transfer-fixing member to form a nip at which the transfer process and the fixing process are performed simultaneously. While a recording medium passes through the nip, a toner image carried by the transfer-fixing member is transferred and fixed onto the recording medium. In other words, while the toner image is transferred from the transfer-fixing member onto the recording medium, heat is applied to the toner image to soften and melt toner particles forming the toner image. Accordingly, the toner particles are formed into a viscoelastic block. Even when the recording medium has a rough surface and the minute gaps are formed between the transfer-fixing member and the recording medium, the viscoelastic block of toner particles is transferred into the minute gaps. As a result, a high-quality toner image may be formed on the recording medium.
Further, in the image forming apparatus in which the transfer process and the fixing process are performed simultaneously, a conveyance path for conveying the recording medium to the nip formed between the transfer-fixing member and the pressing member may be flexibly designed, because the recording medium does not bear an unfixed toner image before the recording medium reaches the nip. By contrast, in an image forming apparatus in which the transfer process and the fixing process are performed separately, a toner image is transferred onto a recording medium in a transfer device and the toner image is fixed on the recording medium in a fixing device. In other words, the recording medium bears an unfixed toner image before the recording medium reaches a nip formed between a fixing member and a pressing member in the fixing device at which the fixing process is performed. Therefore, a conveyance path connecting the transfer device to the fixing device needs to be designed such that the unfixed toner image on the recording medium does not touch the conveyance path.
In the transfer-fixing device in which the transfer process and the fixing process are performed simultaneously, the transfer-fixing member bearing the toner image is heated to melt toner particles forming the toner image. Therefore, the transfer-fixing member may be thick to extend its life. In addition, when the transfer-fixing member is provided in a large, tandem-type image forming apparatus, the transfer-fixing member may have a large circumferential length, decreasing thermal efficiency of the transfer-fixing member. As a result, the transfer-fixing device may consume a great amount of energy.
Moreover, in order to mitigate thermal damage to an image forming device for forming a toner image to be carried by the transfer-fixing member, the transfer-fixing member is cooled after the transfer-fixing process. Thus, the transfer-fixing member is repeatedly heated and cooled. As a result, the transfer-fixing device may consume a great amount of energy for this reason as well.